FM 246P piston

[Royce]

The machinist that has the heads broke his collarbone snowboarding so I have no CCd them yet.   I have a couple references of 352/360 being 10.5 compression but then I also see a 9.7 number..I need to measure the actual rod length and compression height and deck height to see where I am off from the calculated numbers. Might be a stacking of tolerances from crank stroke rod piston and deck

[RJP]

When my buddy rebuilt his 360 horse engine he used a set of ancient NOS Jahns cast pistons I found at a swap meet they were flat top with no valve reliefs and he was very happy with how they worked out.The original pistons that came out of it had been knurled back in the early 60's by a perfect circle knurling machine that leaves a PC logo in the knurling on the skirts,we thought they were pretty cool.The old Jahns pistons were probably heavy as sledgehammers but he was happy and it balanced out OK.Have you done any tricks to the D heads?If you go with the larger valves you may be able to lose a couple of CC's with those.

This brings back some long buried memories. When I bought my 60 Starliner in 1967 I ran the 360hp/352 for about 6-8 months before pulling it and dropping in the 390 short block I had built by a well known local machine shop. When I tore the 352 down it had Jahns cast domed pistons in it. The compression ratio must have been over 12 to 1 as the heads were the heart shaped small chamber "D" heads [59-61cc?] Any thoughts of building a extra engine for my Starliner was trashed as 5 of 8 pistons were cracked at the pin bosses, each one had 3 or 4 cracks in each piston eliminating any ideas of building a spare engine for it or maybe another car.

[gt350hr]

 Probably the result of a "light " pin , heavy piston and too much RPM. Cast "coffee can" pistons were pretty brittle  back then.

[frnkeore]

Here is some info that might help. I know that Ford didn't account for the piston volume, above the first ring so, I omitted that in my CR calculator.

This is what mustangtec says about the C0AE, C & D heads:

C0AE-6090-C
60 352
Valves 2.02 / 1.55"
In port 2.34 x 1.34
Ex port 1.84 x 1.28
73cc

C0AE-6090-D
60 352HP
61-62 390HP    Valves 2.02 / 1.55"
In port 2.34 x 1.34
Ex port 1.84 x 1.28
59.7cc

I don't know how those cc figures where determined but, the 73cc for the C heads, should be about right. Within +/- 1cc. We know the D heads were smaller but, this is the only figure I've seen.

BTW, if anyone is interested, there is a set of D heads for sale, in my area.

These calculated CR's are based on CH that I believe to be accurate for the 300 hp 352, Royce's 1.844 CH and my estimate of the HG volume of the steel shim .030 gasket. Does anyone have any factual info on when the .015 gasket was first used?

The first picture is from my 1960 Service manual publish in '59 so, it doesn't have the 360 HP. Take note of the gasket thickness and value relief, based on Randy's valve relief info and the common Ford flat top of that period.

[427John]

 I was trying to think of a good way to describe the grooves in the sides of the pistons and coffee can is as good as any.Most specs I have seen for D heads usually list a range of 55-59 or 57-61 cc's.

[troublemaker427]

http://www.nhraracer.com/content/general.asp?articleid=46634&zoneid=132

[frnkeore]

http://www.nhraracer.com/content/general.asp?articleid=46634&zoneid=132

Thank you for that link.

The NHRA specs are not Ford, factory specs though. It is a hodge-podge of what NHRA allows you to use and if your building a engine to run in the class, you should build to those or protest to change to Ford specs.

For instance, there is no way you can get 10.6 CR, using those specs with a notched piston. They also are allowing 1.76 (apparently adj rockers) for the HL engines.

[427John]

The strange thing about those NHRA specs. is that it shows the 60 COAE-D heads as 59.6 cc's,while the 61 390HP that uses the same D heads as 56.2 cc's,it also shows the 62 390HP and 6V which uses the C2SE heads and the 406 6V w/C2SE heads at 56.2 and also shows the 63 406 6V C3AE-C heads at 56.2.The C2SE & C3AE-C heads all use a smaller chamber than standard 352 and 390 heads but is definitely larger as cast than C0AE-D they're usually listed as 61-67 cc's.Does NHRA back calculate chamber volumes from listed CR's or do they arbitrarily assign chamber volumes?

[SSdynosaur]

Supposedly, all NHRA Stock Car Guide engine blueprint specs must be received by NHRA from the OEM for the engine and body combination the manufacturer wishes to list for competition. NHRA does not formulate blueprint specifications on their own and whenever the manufacturer decides to not submit specs for any given year/make/model/engine combination then that particular year/make/model/engine combination is not eligible for competition in either Stock or SuperStock Classes or Eliminators or any other class or eliminator that relies on the Stock Car Guide for classification information. All omissions and errors are the responsibility of the submitting manufacturer.

[SSdynosaur]

deleted

[Royce]

I just CCd my D heads. After a cleanup shave they come out at 60.2 cc. I was hoping a little smaller, but the intake valve has a dished head..  No way I can make 10.5 compression with the parts i have.. Might try to cut the heads another .020?

[frnkeore]

Is your intent to compete in class racing?

I think your going to have to verify all your dimensions, including the stroke. I think the best and easiest way to do that now, is to assemble a measured rod and piston, install it and measure the stroke and deck clearance. That will give a true deck height. From what I added up, something is wrong also, those 1.77 piston, will never get you even 10/1.

If your going to class race it, custom pistons with low tension rings, will make it the most competitive. Other wise I would go with the FT pistons, on Summit and cut the tops to 0.00 deck clearance.

[427John]

If you aren't against installing larger valves without dished heads and cut the seats as high as possible that will gain you a little,if your heads have a couple of valve jobs over the years the seats/valve heads may be getting low which will significantly affect chamber volume.The same friend of mine that had the 360hp sunliner once ran a 428CJ in the starliner I currently have he had the heads rebuilt and the guy sank the seats/valve heads with valve job,he couldn't figure out why the engine would fall on its face at ~5000 rpm,after checking everything he finally pulled the heads off and had another machinist check them as soon as he saw them he said the seats are too low and put seats in the heads,when he reinstalled them the engine would pull hard to nearly 6000 rpm.I don't remember the before and after numbers but do remember the chamber volume changed around 3 or 4 cc's from getting the valve heads back up where they belonged.

[Royce]

Not a race motor  just a stock rebuild ... because It is going in a restoration it has all the 360 horse original stuff.. My intention was just for fun and information to build it to factory spec then dyno it .. See how close it actually comes to 360 horse. Right now I am .053 down the hole with an assembled piston and rod..  Using a .015 to .020 gasket.. Right now I calculate right at 10:1.  If I could get the head down to 56cc then I would hit 10.5:1

[427John]

As far as the NHRA specs,sounds like after 1960 Ford was sending NHRA specs that allowed racers to heavily mill their heads and still be legal,I guess they were learning fast at that point.